Usage patterns
〈物〉に序文を書くto write a preface for (a book, etc.)
He wrote a preface for the book.
〈物〉に序文を寄せるto contribute a preface (usually written by someone other than the author)
A famous writer contributed a preface to this book.
序文で〈事〉を述べるto state something in the preface
The purpose of this study is stated in the preface.